Glass-lined pipes

Abstract

A method of producing a glass-lined metal pipe in which an unconsolidated tal or metal alloy powder is loaded into a sealable glass mold comprising a graphite core, a glass sleeve slipped over the graphite core with a sliding fit, a sealable outer glass envelope surrounding the graphite core and glass sleeve forming with them a sealable chamber for the metal or metal alloy powder, wherein the glass is a type which becomes plastic when heated. The air in the mold is removed under vacuum and the mold is sealed and placed into a free flowing refractory powder in a crucible and consolidated by sintering under atmospheric pressure (CAP® process). Removal of the glass envelope and the graphite core produces a glass-lined pipe in which the glass liner is slightly fused into and is under compressive force from the surrounding metal pipe.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A method of producing a glass-lined metal pipe comprising: (a) loading unconsolidated metal or metal alloy powder into a sealable glass mold comprising a graphite core, a glass sleeve slipped over the graphite core with a sliding fit, a sealable outer glass envelope surrounding the graphite core and glass sleeve and forming with them a sealable chamber for the metal or metal alloy powder, wherein the glass is a type which becomes plastic when heated;   (b) evacuating the atmosphere from the metal or metal alloy powder filled chamber in the mold;   (c) sealing the chamber;   (d) placing the mold in an open top refractory container and packing with free flowing refractory powder selected to freely flow at all the temperatures in the process;   (e) heating the mold and the metal or metal alloy contents of the mold to a temperature at which sintering of the metal or metal alloy powder takes place and holding at this temperature for a time sufficient to cause substantially complete densification of the powered metal or metal alloy, during which step the mold is supported by the free flowing refractory powder as the glass sleeve and the glass envelope become plastic and the mold shrinks in volume as its metal or metal contents densify putting pressure against the plastic glass sleeve which is compressed against the solid graphite core;   (f) cooling and removing the glass envelope portion of the mold to leave a composite article comprising the consolidated metal or metal alloy layer, a glass liner under compression from the consolidated metal or metal alloy layer, a very thin interfacial fused layer of glass and metal or metal alloy, and the graphite core; and   (g) removing the solid graphite core from the composite article produced in step (f) to produce the glass-lined metal or metal alloy pipe.   
     
     
       2. The method of claim 1 which further comprises after step (e) but before step (f), transferring the open top refractory container, refractory powder, and mold directly into an insulated, refractory lined covered container and then placing the covered container into a pressure chamber and applying an isostatic pressure of 2,000 psi or more to the mold while it slowly cools down. 
     
     
       3. The method of claim 1 wherein the glass used is a borosilicate glass. 
     
     
       4. The method of claim 1 wherein an unconsolidated metal alloy powder comprising from 38 to 47 weight percent of titanium, from zero to 6 weight percent of an additive metal selected from the group consisting of cobalt, iron, and mixtures thereof, with the remainder of the alloy being essentially nickel. 
     
     
       5. The method of claim 4 wherein the alloy comprises from 42 to 46 weight percent of titanium. 
     
     
       6. The method of claim 4 wherein the weight percent of additive metal in the alloy is zero.